This invention relates generally to electronic control systems and specifically to an electric motor control system including a wiper mechanism that contacts one of a plurality of resistors arranged in a predetermined configuration to generate a motor control signal.
Vehicle rear wiper assemblies have become a standard feature on many present-day motor vehicles. Typically, these rear window wiper assemblies include a wiper blade mounted upon a bracket which is coupled to a wiper arm. The wiper arm is attached to a wiper shaft rotatably driven in a cyclical oscillating manner by a helical gear. A reversible, fractional horsepower, dc electric motor serves to actuate the helical gear through an armature shaft-mounted worm gear enmeshed therewith. This type of rear window wiper arrangement is usually mounted upon a pivoting liftgate of a minivan, station wagon, sport-utility vehicle or the like.
Examples of conventional window wiper assemblies and motor mechanisms are disclosed with the following U.S. Pat. Nos. 4,893,039 entitled "Windshield Wiper Motor" which issued to lsii on Jan. 9, 1990; 4,878,398 entitled "Driving Device for Window Wiper of Motor Vehicles" which issued to Heinrich on Nov. 7, 1989; 4,336,482 entitled "Rear Window Wiper Motor Control" which issued to Goertler et al. on Jun. 22, 1982; 4,259,624 entitled "Arrangement for Wiping a Vehicle Window" which issued to Seibicke on Mar. 31, 1981; 3,694,723 entitled "Motor Vehicle Windshield Wiper Having a Parking Position Outside the Wiper Area" which issued to Schneider et al. on Sep. 26, 1972; and, 3,665,772 entitled "Windshield Wiper Motor Link Depressed Park Mechanism" which issued to Beard et al. on May 30, 1972. All of these patents are incorporated by reference herewithin.
Some conventional vehicles also provide a rear window release lock or latch, actuated by a solenoid, which can be unlocked to allow for upward pivotal movement of the rear window in relation to the otherwise stationary liftgate. In combination therewith, a separate liftgate lock is often mounted upon the liftgate door for fastening the liftgate to the body to prevent inadvertent pivotal opening. This liftgate lock is traditionally operated by manual key or handle rotation, or through a separate electric motor or solenoid.
Additionally, separate motors and solenoids are required to actuate passenger door locks, antenna retraction mechanisms, headlamp cover retraction mechanisms, a fuel filler door lock and other similar functions. This increase in the number of electromagnetic devices has also resulted in the need for motor controllers to control motor operation based on data indicating the particular application being driven by the motor.
Referring to Figure A, present motor control systems include a motor application sensor including a high conductivity copper plate A1 affixed to a motor output, such as the gear A2. Multiple conductive wipers are in contact with the plate and generate motor positional signals, which are output to a motor controller (not shown). Thus, as the plate is rotated, the resistance pattern formed by the plate allows the controller to determine a particular motor application being run.
However, the above described motor control systems have associated drawbacks. For example, it is often difficult for the controller to determine the location of the wipers on the plate if the wipers are both located on an intermediate portion, such as the portion C, as the plate continuity has no variation along such a portion. In addition, conventional motor control systems have difficulty achieving smooth transitions during ramping up or down of motor speed, and often such systems result in abrupt stopping or starting of the motor, which result in motor backlash and wiper wear. Also, the present motor control systems have an associated stopping accuracy that depends directly upon the consistency and inertia of the motor gear output. During low torque/friction applications, the motor runs at maximum speed with high angular momentum. When the supply voltage is discontinued, the motor can continue to rotate several revolutions before stopping. In a heavily loaded, slow system, the stopping would be almost instantaneous resulting in a disparity and final motor position.